Bounce codes › Gmail
553 5.1.2: Address not found, domain couldn't be found
The part after the @ doesn't exist, or it has no mail server. Nobody at that domain can get email, so your message could not be delivered.
Most of the time it is a typo (gmial.com, outlok.com, .con) or a company domain that has expired. Check the domain below.
I sent the email Mail to my own domain bounces
Check the domain that bounced
Type the address or just the domain. See whether the domain exists, whether it can receive email, and whether it looks like a typo.
Try:
Runs in your browser. Only the domain is looked up, through Cloudflare's public DNS. The address is not sent anywhere or stored.
Fix your list Domain cannot receive email
The domain after the @ was not found.
- Sent by: Gmail / Google Workspace
- Permanent (hard bounce). Sending the same message again fails again.
How Gmail words it (source):
We weren't able to find the recipient domain.
Why the domain cannot be found
- A typo in the domain:
gmial.com,hotnail.com,outlok.com, or.coninstead of.com. - A space, comma or extra dot typed into or after the domain.
- The company changed its name or domain, and let the old domain go.
- The domain expired because nobody renewed it.
- The domain exists but email was never set up for it (no mail server).
How the bounce looks in your email tool
Each mail system words it differently. They all mean the same thing: the DNS lookup for the domain after the @ found nothing usable.
| Where you see it | What it looks like (roughly) |
|---|---|
| Gmail (app or web) | Title "Address not found": "Your message wasn't delivered to … because the domain … couldn't be found." Below it: DNS Error: DNS type 'mx' lookup of … responded with code NXDOMAIN |
| Gmail as the sending server (apps, scanners, sending services) | 553 5.1.2 We weren't able to find the recipient domain. |
| Outlook and Microsoft 365 | "The Domain Name System (DNS) reported that the recipient's domain does not exist." In the details: 550 5.4.310 DNS domain … does not exist [Message=InfoDomainNonexistent] |
| Web hosts and own servers (Postfix, cPanel) | Host or domain name not found. Name service error for name=… type=MX: Host not found |
| Your own mail server, before it sends | 550 5.1.2 … Recipient address rejected: Domain not found |
Google's own wording for 553 5.1.2 adds: check for spelling errors, and make sure there are no spaces, periods or other punctuation after the address. 5.1.2 is the standard code for "bad destination system address" (SMTP enhanced status codes). Microsoft does not list 5.4.310 in its NDR table, but its words say the same.
Typo, dead domain or a short DNS hiccup?
| What you see | What it means | What to do |
|---|---|---|
A misspelled domain: gmial.com, gamil.com, outlok.com, yahoo.co, .con, .cmo | A typo. | Fix the address and send again. |
A space, comma or extra dot: jane@company .com, [email protected]. | The stray character became part of the domain. | Retype the address. |
| The domain is spelled right, but the company closed, renamed or moved | The domain no longer exists, or has no mail server. | Remove the address. Ask the person for a new one another way. |
The words say try again, or the code starts with 4 | A passing DNS failure. The domain may be fine. | Wait: your mail system retries. If it still fails after a day, check the domain. |
If you sent the email
- Look at the part after the @ in the bounce, letter by letter, or run the domain check above.
- If it is a typo, fix it and send again. Fix it where the address came from too: your contacts, your CRM, the sign-up form.
- If the domain is spelled right and cannot receive email, remove the address. Sending again bounces again, and repeated bounces hurt your sender reputation.
- If you send newsletters or campaigns, check the whole list before the next send. Typos like
gmial.comand dead company domains are exactly what the email list checker finds, free and in your browser.
Stop typos where they start
If people type their address into a form on your site, most of these bounces start there. Show a "Did you mean gmail.com?" hint, or ask for the address twice. The email typo checker shows which typos are common.
If mail to your own domain bounces like this
Then senders cannot find mail servers for your domain. Check in this order:
- Is the domain still registered? An expired domain drops out of DNS. Check the renewal date at your registrar.
- Does it have MX records? Run the MX record checker. No MX records, or MX records pointing to a host name that does not exist, means senders cannot deliver.
- Did you just change email providers or DNS hosts? The DNS that is now in charge (your current name servers) must hold the MX records your email provider gives you. Changes reach other servers only after the old records expire (their TTL).
- Is DNSSEC set up right? Broken DNSSEC makes lookups fail at providers that check it, while others still work. Your DNS host can test it.
Just bought the domain? A new domain has no MX records until you set up email for it. Buying a domain (at GoDaddy or anywhere else) and buying email are separate steps: in your email provider's setup (Microsoft 365, Google Workspace…) add and verify the domain, then add the MX record it shows you at your DNS host.
If only some senders get the bounce, a recent DNS change has not reached everyone yet, or one of your name servers still has old records.
Not the same as
| Code | What it means | Whose move |
|---|---|---|
| 550 5.1.1 | The domain is fine, but the mailbox before the @ does not exist. | You: fix or remove the address |
| 550 5.4.1 | Microsoft 365 knows the domain, but not that address. | You, or their IT |
4.4.7 Message expired | The domain exists, but its mail server did not accept the message in time. | Their side; try again later |
556 5.1.10 null MX | The domain says on purpose that it never receives email. | You: remove the address |
Questions
Is "domain not found" a hard bounce?
Yes, when the code starts with 5: the domain does not exist, and sending again fails again. If the message says "try again" or the code starts with 4, it was a short DNS failure and your mail system retries by itself.
The website works. Why does email say the domain doesn't exist?
If the website opens, the domain exists. Check that the address has exactly the same domain (.co and .com are different domains, so is one missing letter). If it does match, the domain may have no mail server: run the domain check.
What does NXDOMAIN mean?
"Non-existent domain." It is what DNS answers for a name that is not registered or not set up. Mail cannot be delivered to it.
What is 5.4.310 in Outlook?
Microsoft 365 uses it when the DNS lookup says the recipient's domain does not exist. Microsoft does not list it in its NDR table; the words after it, DNS domain … does not exist, are the explanation.
Can I just send it again?
Only after you fix the address. The same address bounces again. The exception is a temporary DNS failure: "try again", or a code starting with 4.
Can I check a whole list for dead domains?
Yes. The email list checker looks up every domain in a list, marks the ones that do not exist or cannot receive email, and suggests fixes for common typos. It runs in your browser; the list is not uploaded.
Got a different bounce?
Paste the whole message into the bounce code lookup. It reads the code and the words and tells you whose move it is.
Related codes
550 5.1.1The email account that you tried to reach does not exist (Gmail)550 5.4.1Recipient address rejected: Access denied (Microsoft 365)550 5.1.10Recipient not found (Microsoft 365)
Free tools
Checked on 2 Nov 2026 against Google's Gmail SMTP errors and codes (553 5.1.2, updated 26 Oct 2026), Microsoft's NDR list for Exchange Online (5.4.310 is not in it) and the SMTP enhanced status codes. The wording from the Gmail app, Outlook and Postfix is shown as these programs print it and can differ slightly by version.